How do I manipulate column formulae in data tables by scripting?

[#1]

Hi, 

I'm trying to add a formula to convert values in a selected column through scripting without having to add any new columns in the data table, is there a way to edit formulas for a column by scripting? For example I'm trying to set the height column in this data table to be halved when I run the script:

Names Default To Here( 1 );
Open( "$SAMPLE_DATA/Big Class.jmp" );
Current Data Table() << Get Column Names;
height = height/2;

[#2]

A data column formula is just a JSL expression that is evaluated row-wise. You can use the data column messages << Get Formula() and << Set Formula(). Use expression functions to access and modify the expressions as needed.

[#3 · Accepted solution]

Your specified formula is recursive when used as a column formula.  A column formula will run whenever it detects a change in the column.

What you are suggesting can simply be done in open JSL.

Names Default To Here( 1 );
Open( "$SAMPLE_DATA/Big Class.jmp" );
Current Data Table() << Get Column Names;
height = height/2;

or

Names Default To Here( 1 );
Open( "$SAMPLE_DATA/Big Class.jmp" );
For( i = 1, i <= N Rows( current data table() ), i++,
	:height[i] = :height[i] / 2
);

or

Names Default To Here( 1 );
dt = Open( "$SAMPLE_DATA/Big Class.jmp" );
dt:Height << set values( dt[0, 4] / 2 );

If the formula isn't recursive, one can set the column formula by using the Set Formula message

Names Default To Here( 1 );
Open( "$SAMPLE_DATA/Big Class.jmp" );
Current Data Table() << Get Column Names;
:height << set formula(:weight/2);

I strongly suggest that you take the time to read the Scripting Guide available in the JMP Documentation Library under the Help pull down menu